Subshtuted amino)phenyl]
morpholines

ABSTRACT

ANTIOZONANTS OF THE FORMULA   4-(4-(R-N(-X)-)PHENYL)MORPHOLINE   WHERE X IS (HYDROGEN OR) NITROSO AND R IS ALKYL OF 3 TO 12 CARBON ATOMS OR CYCLOALKYL OF 5 TO 12 CARBON ATOMS ARE NEW COMPOUNDS USEFUL FOR PROTECTING NATURAL AND SYNTHETIC RUBBERS FROM OZONE DEGRADATION.

United States Patent Matter enclosed in heavy brackets [1] appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE Antiozonants of the formula CHzCHZ where X is[hydrogen or] nitroso and R is alkyl of 3 to 12 carbon atoms orcycloalkyl of 5 to 12 carbon atoms are new compounds useful forprotecting natural and synthetic rubbers from ozone degradation.

This invention relates to a new method for protecting rubber fromdegradation and to new compounds having special significance asantidegradants. More particularly, the invention relates to4-[p-(substituted amino)pheny1] morpholines and their use in rubberagainst ozone attack.

An object of this invention is to provide new chemical compounds whichhave special significance as antiozonants in rubber. A further object ofthis invention is to provide a method for the protection of rubberagainst ozone attack. Other objects of this invention will becomeapparent as the description proceeds.

Degradation of rubber products by ozone has been a recognized problemfor a considerable time in the rubber industry. However, the rubberindustrys use of rubber chemicals as antiozonants spans only the lasttwo decades. Before this time, wax was the most used rubber protectoragainst ozone attack. Wax is used today as an antiozonant, but isusefulness is limited. Although wax is an efiective antiozonant forrubber not subject to abrasion, viz static, it is not as useful inrubber exposed to active use, VIZ dynamic. The chemical industry hasattempted to provide antiozonants for rubber useful under both staticand dynamic conditions. Santoflex AW, the Monsanto trademark for6-ethoxy-l,2-dihydr0-2,2,4-trimethylquinoline, is one'of the firstchemicals developed as a rubber antiozonant. Various phenylenediamineshave also been explored and developed as rubber antiozonants.

In United States Patent 1,899,058, Re. 19,654, Rubber Composition andMethod of Preserving Rubber, Reed to B. F. Goodrich Co. (1932), various4-phenyl morpholines are disclosed as antioxidants or age-resistors. Thehydroxy substituted aromatic nucleus appear to be the most valuable.according to the Reed patent. Reeds disclosure includes such compoundsas 4-(p-amino phenyl) morpholine and 4- [p- (dimethylamino phenyl] -2,6-dimethyl morpholine. We have discovered that compounds, for example4-[p-(isopropylamino)phenyl]morpholine, 4[p-1-methylpropylamino)phenyl]morpholine, 4[p-(1,3dimethylbuty1amino)phenyl1morpholine, 4-[p-(1,4-dimethylpentylamino)phenyl]morpholine, 4 [p-(lethyl 3methylpentylamino)phenyl]morpholine, 4-{p- (1methylbutylamino)phenyl]morpholine, 4 [p-(cyclo- Re. 27,311 ReissuedMar. 21, 1972 hexylamino)phenyl]morpholine and 4-[p-N-isopropyl-N-nitrosoamino)phenyl]morpholine have special significance when tested asantiozonants simultaneously with the Reed compounds. The compounds ofthis invention have special significance in rubber over the Reedcompounds because the compounds of this invention are superiorantiozonants. These superior antiozonant properties of the compounds ofthis invention are demonstrated in the tables, infra.

To prepare 4-[p-(isopropylamino)phenyl]morpholine, 94 grams (0.45 mole)of 4-(p-nitrophenyl)morpholine, 200 grams of acetone, 1 gram of glacialacetic acid, grams of methyl alcohol and 1 gram of 5% platinum on carbonin 15 ml. of benzene are charged to a l-liter stainless steel autoclave.The autoclave is sealed and purged twice with nitrogen. The stirredreaction mixture is reduced with hydrogen at 40 C. to C. and 250 to 400lbs. pressure per square inch, gauge over a 1.5 hour period or until atheoretical amount of hydrogen is absorbed. After cooling to 60 C. thecatalyst is removed by filtration. The filtrate is added to 2000 gramsof ice water and stirred at 0 to 10 C. for 1 hour. The solids arecollected by filtration, washed with 200 ml. of water and air dried at25 to 30 C. The 4-[p-(isopropylamino)phenyl] morpholine, melting point103-104 C., is obtained in 71% yield. After recrystallization fromheptane, the product melts at 104105 C. Nitrogen analysis of the productis 12.65% nitrogen compared to 12.72% nitrogen calculated for C H N O.Comparable results are obtained when the starting material4-(p-nitrophenyl)morpholine is replaced with4-(p-nitrosophenyl)morpholine.

To prepare 4-[p-(1-methylpropylarnino)phenyl]morpholine, 89 grams (0.44mole) of 4(p-nitrophenyl)morpholine, 225 grams of methyl ethyl ketone,1.5 grams of glacial acetic acid, 75 grams of methyl alcohol and 2.2grams of 5% platinum on carbon in 15 ml. of benzene are charged to a1-liter stainless steel autoclave. The autoclave is sealed and purgedtwice with nitrogen. The stirred reaction mixture is reduced withhydrogen at 40 to 120 C. and 250 to 400 pounds pressure per square inch.gauge over a 1.5 hour period or until a theoretical amount of hydrogenis absorbed. After cooling to 60 C., the catalyst is removed byfiltration. The filtrate is added to 2000 grams of ice water and stirredat 0 to 10 C. for one hour. The solids are collected by filtration,washed with 200 ml. of water and air dried at 25 30 C. The 4-[p-(1-methylpropylamino)phenyl1morpholine, melting point 8889 C., is obtainedin 74% yield. The melting point remains unchanged afterrecrystallization from heptane. Nitrogen analysis of the product is11.89% nitrogen compared to 11.96% nitrogen calculated for C H N O.Comparable results are obtained when the starting material4-(p-nitrophenyl)morpholine is replaced with4-(pnitrosophenyl)morpholine.

To prepare 4-[p-(1,3-dimethylbutylamino)phenyHmorpholine, 41.6 grams(0.2 mole) of 4-(p-nitrophenyl)morpholine, grams of methyl alcohol, 100grams of methyl isobutyl ketone, 1 gram of glacial acetic acid and 1.5grams of 5% platinum on carbon in 20ml. of benzene are charged to a1-liter stainless steel autoclave. The autoclave is sealed and purgedtwice with nitrogen. The stirred reaction mixture is reduced withhydrogen at 30 to 126 C. and 150 to 300 pounds pressure per square inch,gauge over a 4.5 hour period or until a theoretical amountof hydrogen isabsorbed. After cooling to 60 C., the catalyst is removed by filtration.The benzene, methyl alcohol and excess methyl isobutyl ketone areremoved in vacuo at a maximum temperature of 178 C. at 2 mm. Hg. Theproduct solidifies when cooled. The 4-[p-(l,3-dimethylbutylamino)phenyl]morpholine, melting point 6165 C., is obtained in 99%yield. The melting point is 63.5

55.5 C. after recrystallization from ethyl alcohol. Nitrogen analysis ofthe product is 10.62% nitrogen compared 10.68% nitrogen calculated for CH N O.

To prepare 4-[p-(1,4 dimethylpentylamino)phenyl] norpholine, 62.4 grams(0.3 mole) of 4-(p-nitrophenyl) norpholine, 50 grams of methyl alcohol,150 grams of nethyl isoamyl ketone, 1.0 gram of glacial acetic acid ind1.5 grams of platinum on carbon in 20 ml. of Jenzene are charged to a1-liter stainless steel autoclave. ['he autoclave is sealed and purgedtwice with nitrogen. The stirred reaction mixture is reduced withhydrogen It 58 C. to 127 C. and 90 to 330 pounds pressure per :quareinch, gauge over a 3-hour period or until a theoetical amount ofhydrogen is absorbed. After cooling to 30 C., the catalyst is removed byfiltration. The benzene, nethyl alcohol and excess methyl isoamyl ketoneare renoved in vacuo at a maximum temperature of 190 C. at i mm. Hg. Theproduct solidifies when cooled. The 4- p (1,4dimethylpentylamino)phenyl]morpholine, meltng point 52 -58 C., isobtained in 99% yield. The prodict melts at 58.0-59.5 C. afterrecrystallization from :thyl alcohol. Nitrogen analysis of the productis 9.78% iitrogen compared to 10.14% calculated for C H N O.

To prepare 4-[p-(1-ethyl-3-methylpentylamino)phenyl] norpholine, 62.4grams (0.3 mole) 4-(p-nitrophenyl)moriholine, 50 grams of methylalcohol, 250 grams of 5- nethyl-3-heptanone, 1.0 grams of glacial aceticacid and ..5 grams of 5% platinum on carbon in 20 ml. of benzene irecharged to a l-liter stainless steel autoclave. The auto- :lave issealed and purged twice with nitrogen. The stirred 'eaction mixture isreduced with hydrogen at 45 to 134 3. and 200 to 400 pounds pressure persquare inch, gauge wer a 4-hour period or until a theoretical amount of\ydrogen is absorbed. After cooling to 60 C., the cat- Llyst is removedby filtration. The benzene, methyl alco- I01 and excess5-methyl-3-heptanone are removed in vacuo Lt a maximum temperature of204 C. at 5 mm. Hg. The )roduct solidifies when cooled. The4-[p-(l-ethyl-3-meth- 'lpentaylamino)phenyl]morpholine, melting point 55i0 C., is obtained in 97.5% yield. The product melts at i566 C. afterrecrystallization from heptane. Nitro- ;en analysis of the product is9.10% nitrogen compared 0 9.65% nitrogen calculated for C H N 0.

The preparation of 4-[p-(l-methylbutylamino)phenyl] norpholine issubstantially the same as the preparation If 4-[p-(1-ethyl 3methylpentaylamino)phenyl]morre collected by filtration, washed withWater until the lashings are neutral to litmus and air dried at 25 to 0C. The 4-[p-(l-methylbutylamino)phenyl]morphoine, melting point 8081 C.,is obtained in 99% yield. The melting point is unchanged afterrecrystallization rom heptane. Nitrogen analysis of the product is11.30% .itrogen compared to 11.28% nitrogen calculated for :15 24 2 Thepreparation of 4-[p-(cyclohexylamino)phenyl] ."lorpholine issubstantially the same as the preparation of -[p-(1-ethyl 3methylpentylamino)phenyl]morpholine .escribed above, exceptcyclohexanone is used as a startag material instead of5-methyl-3-heptanone. The catalyst i removed from the product byfiltration. The filtrate is ooled to 0 C., and the resulting solids arecollected by .ltration and air dried at 25 to 30 C. The 4-[p-(cyclo-.exylamino)phenyl]morpholine, a white solid melting at 28 -1 29 C., isobtained in 69.5% yield. Nitrogen analyis of the product is 10.83nitrogen compared to 10.76% itrogen calculated for C H N 0.

To prepare 4-[p-(N-isopropyl-N-nitrosoamino)phenyl] iorpholine, astirred charge containing 44 grams (0.2 mole) of 4-[p-(isopropylamino)pheny1]morpholine in :00 m1. of isopropyl alcohol is heated to 50 C. forsolution. After cooling to 25 C., 28 grams (0.28 mole) of concentratedhydrochloric acid is added at 25 to 30 C. over a five-minute period. Tothis stirred solution, 15.4 grams (0.22 mole) of 98% sodium nitrite in30 ml. of water is added subsurface at 25 to 30 C. over a period of 15minutes. After stirring at 25 to 30 C. for l'hour, 6 grams ofconcentrated ammonium hydroxide in 600 ml. of water is added, andstirring is continued for 15 minutes. The solids are collected byfiltration, washed with water until the washings are neutral to litmusand air dried at 25 to 30 C. The 4-[p-(N-isopropyl-N-nitrosoamino)phenyl]morpholine, a melting point 7779 C., is obtained in 94.4% yield.A melting point of 89-90 C. is obtained after recrystallization fromethyl alcohol. Nitrogen analysis of the product is 16.38% nitrogencompared to 16.86% nitrogen calculated for C H N O.

Rubber ozone resistance data for the compounds of this invention arereported in the following tables. The method used for measuring theozone damage to vulcanized rubber is described by Decker and Wise, TheStress Relaxation Method for Measuring Ozone Cracking, Rubber World,April 1962, p. 66. The equipment used in these tests is comprised of aBlue M Oven used as an ozone cabinet. This is a product of the Blue MElectric Company of Blue Island, 111. The cabinet is modified withHanovia ozone generating equipment. Six quartz lamps are installed inthe air chamber beneath the oven floor. The ozone concentration in thecabinet is controlled with the lamps. The ozone concentration in thechamber can be controlled withiniS from 10 to 200 parts. per hundredmillion parts of air. The cabinet is equipped with a rack for statictesting and one for dynamic testing. The static rack handles 12 stocksat strains of 5, 10, 20, 30 and 40%. The dynamic tester is a reciprocalmechanism which imparts a 25% strain to the rubber test pieces. The topplate of the dynamic tester moves up and down, and the bottom plate isstationary. The tester is driven at a rate of 90 cycles per minute by agear motor mounted on the outside of the cabinet. The test pieces ofrubber are two-inch long T-50 (ASTM D 599-55) specimens dried fromstandard stress strain test sheets (ASTM D 15-57T). They are mounted byplacing their ends in the radical slots milled into the edges of thecircular plates of the racks. The tab ends fit into the circumferentialgrooves machined into the outer surfaces of the plates.

The stress relaxation method is based on the principle that theeffective cross-sectional area of a small test piece of rubber isreduced by ozone cracking. The extent of cracking in a test piece isdetermined by measuring the forces required to extend the test piecebefore and after exposure to ozone. As the strip begins to crack, thenumber of stress-supporting rubber chains decreases, and the forcerequired to extend the strip 100% is reduced. The ratio of this force tothe original force is calculated at approximately sixteen-hour intervalsof exposure to ozone. The graph of force vs. time is essentially astraight line, and the time required for attaining 90%, 80%, and 70% ofthe original force is readily determined from the graph. The ability ofthe rubber to resist ozone attack is obtained by comparison of thesenumbers. These ratios are the percent of original modulus of the rubbertest piece and are listed as percent retention in the tables, infra. Theozone concentration for the tests is 25 parts ozone per hundred millionparts of air. Longer times in the data demonstrate better ozoneresistance of the rubber stock. The intermittent test comprises two-hourcycles during which the specimens are exposed dynamically 15% of thetime and during the remaining time of the cycle are exposed staticallyat 25 strain.

The stocks of Table I are vulcanized rubber stocks comprised of a B-lSBR base stock containing 100 parts styrene-butadiene rubber 1500, 50parts Philblack O which is high abrasion furnace carbon black, 4 partszinc oxide, 2 parts stearic acid and 10 parts Necton 60 which is ahydrocarbon softener. Added to the base stock are 1.0 part Santocure NSwhich is the accelerator N-tert.-buty1- 2-benzothiazolesulfenamide, 1.75parts sulfur and 2 parts of the listed antiozonant.

The stocks of Table I contain the following antiozonants:

1 2 3 4 (hr.) (hrs) (his) (hrs) morpholine, and stock 4 is the compound4- [p-(dimethylamoino)pheny1] 2,6-dimethyl morpholine. The naturalrubber masterbatch for the stocks of Table II is an A-l base stockcomprised of 100 parts natural rubber, 50 parts high abrasion furnaceblack, 3 parts stearic acid, 5 parts zinc oxide and 3 parts hydrocarbonsoftener. Other additives are sulfur in 2.5 parts of Santocure NS in0.50 part. The concentration of the antiozonants is 2.0 parts.

TABLE II Stocks 1 2 3 4 (hr.) (hrs.) (hrs.) (hrs.)

Unaged dynamic ozone resistance:

90 percent retention 8 26 22 14 80 percent retention 15 64 56 48 70percent retention 23 92 92 93 Unaged dynamic ozone resistance 90%retentiom- 5 31 80% retention- 11 52 70% retention 18 70 Unaged staticozone resistance 90% retention 2 10 80% retention 7 27 70% retention 1247 Aged d namio ozone re time 90 0 retention 6 22 80% retention 12 4470% retention 18 64 Aged static ozone resistan 90 0 retent n 3 10 80%retention 9 21 70% retention 14 37 Unaged intermittent ozone resistance:

90% retention 2 21 80% retention 7 47 70% retention. 12 67 Agedintermittent ozone resistance:

90% retention 3 16 80% retention... 9 34 70% retention 14 54 Stock 5 6 7(hrs.) (hrs.) (hrs) By totaling the number of hours that a rubber stockretains the described percentages of the stocks Original modulus, acomparison of the stocks can be made. These comparisons illustrate thespecial significance of the compounds of this invention. While thecompound of stock 7 shows 94 hours total under unaged dynamicconditions, in contrast 4-[p-(isopropylamino)phenyl]morpholine of stock2 demonstrates that it takes 153 hours to deteriorate the rubber to thesame degree under the same conditions. This is a 63% increase ineiiiciency over the compound of stock 7. The compound4-[p-(1-methylpropylamino)phenyl]rnorpholine of stock 3 demonstrates a78% increase in efficiency over stock 7 under dynamic conditions. Theremaining stocks demonstrate the following percentage increases inetficiency under unaged dynamic conditions over stock 7: Stock 4,4-[p-'(1,3-dimethy1butylamino)phenyl]morpholine, 55%; stock 5,4-[p-(1,4dimethylpentylamino)phenyl1morpholine, 50%; and stock 6, N-[p-( l-ethyl 3 methylpentylamino)phenynmorpholine, 47%. The specialsignificance of the compounds of this invention, as compared to thecompound of stock 7, is demonstrated more dramatically by comparison ofthe data for the aged dynamic ozone resistance tests. The percentageincreases in efficiency of the antiozonants of this invention over stock7 in aged dynamic ozone resistance tests are as follows: Stock 6, 99%increase; stock 5, 84% increase; stock 4, 84% increase; stock 3, 100%increase; and stock 2, 84% increase.

Table II illustrates the special significance of the compounds of thisinvention when used as antiozonants in natural rubber. The unageddynamic properties of two compounds of this invention are shown in TableII. Stock 1 is a blank. Stock 2 is 4-[p-(isopropylamino)phenyl]rnorpholine, already shown to have specialsignificance in Table I. Stock 3 is 4-[p-(l-methylpropylamino)phenyl]TABLE III Stocks 1 (hr.) 2 (his? sih 5.2533255232322 25 2s 31 percentretention 70 percent retention Table III illustrates that stock 1containing 4-[p-(cyclohexylamino)phenyl]morpholine, is an even moreefiicient antiozonant than the compound of stock 2,4-[p-(isopropylamino)phenyl]morpholine, under unaged dynamic conditions.

The compound 4-[p-(N-isopropyl N nitrosoamino) phenyl]morpholine of thisinvention demonstrates comparable antiozonant properties to the highlyeifective 4-[p- (isopropylamino)phenyl1morpholine also of thisinvention. Table IV illustrates the comparison of the two compounds. Thenatural rubber stocks are A-l base stocks described, supra. The naturalrubber stocks contain the additives sulfur in 2.50 parts per hundredrubber and Santocure NS in 0.50 part. The antiozonant concentrations are1.5 parts. The SBR stocks are B-l base stocks described, supra. Theadditives in the SBR stocks are 1.75 parts sulfur per hundred partsrubber and 1.0 part Santocure NS. The antiozonant concentrations are1.50 parts.

Stock 1 is a blank, stock 2 is 4-[p(N-isopropyl-N-nitrosoamino)phenyl]morpholine, and stock 3 is 4-[p-(isopropylamino )phenyl] morpholine.

TABLE IV Stocks 3 (hr (hrs.) (hrs.)

Natural rubber:

Unaged dynamic ozone resistance:

90 percent retention 2 9 10 80 percent retention 27 26 70 percentretention 9 57 51 Unaged static ozone resistance:

90 percent retention 1 7 7 80 percent retention 3 18 18 70 percentretention 7 39 39 SB R:

Unaged static ozone resistance:

90 percent retention 3 11 12 80 percent retention 7 22 26 70 percentretention 12 37 40 Unaged static ozone resistance 90 percent retention 17 5 80 percent retention 2 12 11 70 percent retention 6 18 20 Thegeneral formula for the antiozonants of this invention is:

where X is hydrogen or NO, R is alkyl or 3 to 12 carbon atoms butpreferably 3 to 8 or R is cycloalkyl of 5 to 12 carbon atoms. Theantiozonants of this invention are effective in amounts as low as 0.2part per hundred rubber. The concentrations can range as high as partsper hundred rubber, but concentrations of 1.5 to 3 parts are preferred.Antiozonant properties comparable to those illustrated in natural rubberand SBR are obtained with oil extended styrene-butadiene rubber,cis-4-polybutadiene, butyl rubber, ethylene-propylene terpolymcrs,polymers of 1,3-butadiene, for example 1,3-butadiene itself, and ofisoprene and copolymers of 1,3-butadiene with other monomers, forexample styrene acrylonitrile, isobutylene and methyl methacrylate.

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is: I

1. A compound of the formula wherein X is [H or] NO; and wherein R issecondary alkyl of 3 to 12 carbon atoms or cycloalkyl of 5 to 12 carbonatoms.

[2. 4 [p (isopropylamino)phenyl1morpholine of the [3.4-[p-(l-methylpropylamino)phenyl]morpholine of the formula [4. 4[p-(1,3-dimethylbutylamino)phenyl]morpholine of the formula formula H 0N N 6. 4-[|p-N-isopropyl N nitrosoamino)phenyl]morpholine of the formula[7. 4- [p-(l methylbutylamino)phenyl]morpholine 0f the formula CH CH CHReferences Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 1,937,844 12/1933 Reed -88 1,915,334 6/1933Salzberg et a1. 260-243 2,075,359 3/1937 Salzberg et a1 16722 JOSETOVAR, Assistant Examiner US. Cl. X.R. 260-458, 814

